1. Field of the Invention
The present invention relates to a communication system, a communication apparatus, and a control method thereof.
2. Description of the Related Art
Conventional multi-channel speaker systems are used with apparatuses such as a digital television set, a DVD player, and an AV amplifier to form a home theater. An example of a typical home theater is shown in FIG. 11. Reference numeral 1101 denotes a digital television set and 1102 denotes a DVD player. Reference numeral 1103 denotes an audio and video amplifier and reference numerals 1104 through 1109 denote six speakers forming a 5.1-channel surround sound system. For example, reference numeral 1104 denotes a subwoofer, 1105 denotes a center speaker, 1106 denotes a main left channel speaker, 1107 denotes a main right channel speaker, 1108 denotes a rear left channel speaker, and 1109 denotes a rear right channel speaker.
Requirements for audio data reproduction in a surround sound system include management of reproduction time. US2004-010727 (corresponding to Japanese Patent Laid-Open No. 2003-037585) proposes a method in which a time information delivery means is provided on a network, and speakers adjust their internal clock frequencies based on time information they received to determine the exact time and generate a synchronization signal based on a timestamp in audio data they received. Japanese Patent Laid-Open No. 2001-275194 proposes a method in which audio data to which a synchronization signal is added is transmitted at regular time intervals and speakers reproduce and output audio data based on the timing at which the synchronization signal is detected.
However, these methods require dedicated receiving circuits for generating and detecting synchronization signals. Another problem is that, when an audio source is changed, initial setting values for the receiving circuits must be re-set for each speaker, which adds a load on communication and control processing.